Command line operations (replace asmdef/assemblies, change execution order, build)

Hi,

These are some operations that we created scripts and command line options for in our projects in order to enable more advanced integration and operations of Unity with our Continuous Integration pipeline and I feel that they could be native to Unity and useful to other users that create packages

• Replace asmdef/assemblies replaces asmdef files with their assembly equivalent. This allows us to generate packages with assemblies instead of script files that can be opened. This was a difficult one as we had to keep track of assets ids in order to put them back to the assemblies
  
• Change execution order changes the execution order of monobehaviours. This is used in conjunction with the previous command so that some key behaviours in our assemblies have the right execution order value
• Build builds an executable from a scene with multiple options (scenes, runtime, target, ....). Overall, I feel like the Unity editor would be more suited to automatic batch mode operations if all build parameters could be changed from command line